1. Field of the Invention
The present invention relates to a data transfer method for transferring data with address buses, a data transfer program storage medium in which this data transfer method is stored, and information processing equipment, a card-shaped medium and an external storage medium to be used in the data transfer method.
2. Description of the Prior Art
Recently, to expand the possibility of information processing equipment such as personal computers, PC cards have been proposed. The PC card is a card-shaped medium, and when used, it is inserted in an exclusive slot provided in a personal computer. A PC card, when inserted into the slot, is connected to the personal computer via a data bus and an address bus. PC cards are available in various kinds such as those which function as a storage medium and those which act as an interface with equipment connected to external. The user is allowed to make use of the function of an inserted PC card in a personal computer only by changing the PC card to be inserted into the slot. Thus, it has been becoming possible to expand and change the functions of personal computers simply and readily.
However, currently common PC cards are to be connected to personal computers with a 16-bit long data bus, being capable of transferring only 16-bit data at a maximum in 1-cycle data transfer. As a result of this, there has been an issue that long time would be taken from start to end of data transfer when the volume of the data to be transferred is as large as 64 Kbyte or so.
Meanwhile, in some personal computers, larger capacity of memory space that can be specified with the address bus is allocated relative to the actually installed memory capacity. In such equipment, it is seldom the case that the whole address bus is used, and there exist, in most cases, address bus bit lines that are not used but idling. With attention given to this fact, there have been proposed methods for transferring data by using these idling address bus bit lines (Japanese Patent Laid-Open Publications SHO 56-143049, SHO 61-184655, SHO 62-254050 and HEI 2-23045).
However, since these methods use the idling address bus bit lines for data transfer, the amount of data which can be transferred using the address bus varies depending on the number of bits (free capacity of the address bus), as a problem. Moreover, there has been another problem that the data transfer method could not be executed if no idling address bus bit lines are present (when the address bus has no free capacity).
An object of the present invention is to provide a data transfer method which, in data transfer, allows part of the data to be transferred anytime by using the address bus, thus having accomplished a reduction in time required for data transfer.
Another object of the present invention is to provide a data transfer program storage medium in which programs for executing the above data transfer method are stored, and information processing equipment serving as a transfer source, as well as a card-shaped medium and an external storage medium serving as transfer destinations when this data transfer method is executed.